What do you guys do about mutons and their endless grenading? I mean, in some maps your troops simply need to be close together, but then a pack of 3 mutons appear, throw three grenades. That appears to take out a few soldiers dead and/or panicked, plus a large area without cover. Then another group of 3 mutons appears. Rinse and repeat, squad dead.
Then of course the cyberdisk shows up and takes out anything he wants everytime.
I have limited experience with mutons, but from what I have seen? Because of the grenades and their high damage weapons, there's no real safe way to fight mutons. On top of that, their high defense means they'll be very hard to hit, especially in cover. You're going to suffer in a drawn out fight, and if both sides are sticking to cover that's what you'll get. So get rid of their cover. Destroy it, flank them or move in close, or use very likely to hit weapons like snipers at a range or multiple explosives. Unleash everything you have, and kill them a fast as possible. Late game
mind control the shit out of them. In multiplayer at least, they have a quarter of a rookie's willpower, if you can't mind control that you can't mind control anything.
Mutons don't generally throw their grenades at me unless I let them live for a few turns. If they're just throwing them immediately for you, I'm not sure what to tell you except put a rookie with really good armor in front and hope it takes all of their grenades to kill him.
Also, the difficulty of missions seems to be determined by panic level + difficulty level + time passed. So playing classic mode like most of us are, once you hit a certain point most missions are going to be "very difficult".